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Precision Automatic Digital Voltmeter

IP.com Disclosure Number: IPCOM000094587D
Original Publication Date: 1965-Mar-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 52K

Publishing Venue

IBM

Related People

Smith, JT: AUTHOR

Abstract

The upper drawing shows a voltmeter. A known voltage source creates a known voltage gradient in potentiometer 10. Servomotor 12 is connected between the unknown voltage and wiper arm 14 of potentiometer 10. Motor 12 moves wiper arm 14 until a balance is achieved between the unknown voltage and the output of potentiometer 10. The output of motor 12 also drives encoder 16. The output of encoder 16 reflects the position of wiper arm 14 and, hence, the value of the unknown voltage.

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Precision Automatic Digital Voltmeter

The upper drawing shows a voltmeter. A known voltage source creates a known voltage gradient in potentiometer 10. Servomotor 12 is connected between the unknown voltage and wiper arm 14 of potentiometer 10. Motor 12 moves wiper arm 14 until a balance is achieved between the unknown voltage and the output of potentiometer 10. The output of motor 12 also drives encoder
16. The output of encoder 16 reflects the position of wiper arm 14 and, hence, the value of the unknown voltage.

The lower drawing shows an optical arrangement of the upper voltmeter. Optical potentiometer 20 has resistor element 21 separated from conductive element 22 by photoconductive material. The wiper arm for potentiometer 20 is a beam of light 23. A servomotor 28 is provided. Motor 28 has a mirror attached to it and thus controls the position of light beam 23. Motor 28 is connected between the output of the potentiometer 20 and the unknown voltage. Light beam 23 is thus moved to a balance position.

Light beam 23 also actuates optical encoder 32. This provides a coded output indicative of the position of beam 23. Encoder 32 consists of a continuous conductive strip 35 and a plurality of intermittent strips 36. All pieces of each intermittent strip 36 are connected by a wire. Strip 35 is separate from strips 36 by photosensitive material. Light beam 23 selectively makes a conductive path from strip 35 to selected strips 36. Hence, the appropriate outputs are...